Method of starting induction motors and apparatus therefor



July 26,1927.

H. O. BREE METHOD OF STARTING INDUCTION MOTORS AND APPARATUS THEREFOR A- FT g l6 Zl' z y 47- 2% v5 22x c Filed July 15, 1926 nae:

MW/wk Q Bree mrentow Patented my 26, 1927.

'HEIIIEB OBWALD BREE, OF AUCKLAND, NEW ZE ALAND.

METHOD STARTING INDUCTION MOTORS AND APPARATUS THEREFOR.

Application filed July 15, 1926, Serial No. 122,655, and in New Zealand August 19, 1925.

' This invention relates to starting methods and apparatus for three phase A. C. induction motors and while especially applicable to the squirrel cage type of such motors may also be utilized with obvious adaptations for other three phase A. C. motors.

The objects aimed at by this invention are to provide an improved power factor over the whole starting eriod with consequentialless use of current or same startin torqueto lessen the starting current at hot star and delta positions com ared with'presentstardelta switches an to allow of starting against greater load than same,to lessen the manufacturing cost as compared with that necessitated by auto'transformer starters, to enable resistances to be shaped and placed so as to allow of starter dimensions being less than equal in size to other ty es, to facilitate repairs, and to enable easy a aptation of the starter to starting conditions,

bythe insertion ofsuitable resistances as required. Other objects are hereinafter reerred to. p My method makes use of the advantages of each of the two known startin namely (1) star to delta switchm which method is to connect the motorjwin ings in star at starting and in delta at running, (2) stator resistance method in which resistances are included in series with each phase of the su ply and are gradually short circuited.

' e starting described takes advantage of 1 the reduction of pressure to the motor .winding and proportionate increase of current by star starting position (2) the use of resistances in each phase or only two phases of the supply whichmay be-cut outrby one or more steps. The use of resistance reduces the starting current. to allowable values and also, which is important, improves the power factor at starting thereby. increasing the startin torq'ue for a given current. Thus a squirre cage motor will have a greater start-' ing torque when certain resistances'are in series with the supply, than when it is directly connected to the mains notwithstandingthat the starting current is less. Further all or some of the resistances may be inserted in the delta position, finally 'being I, cut out. x

This eliminates the heavy rush of current which may occur at switching from star to squirrel cage motors and will in A leading feature of my invention is therefore the use of resistances in conjunction with star delta switching Another leading feature of my invention is the mode of switching hereinafter de scribed which is necessary to give effect to the features above set forth whatever may be the mechanical means employed.

My invention consists in these features and in the features and combinations and arrangements of parts hereinafter described with reference to the accompanying drawings and claimed.

se drawings illustrate a constructional .embodimentof the idea or principle underlymethods in ,my invention, wherein the switchin is e vected by a starter of a drum contro ler type.

- In these drawings Figure 1 is a sectional elevation of my apparatus, Figure 2 is a sectional plan view on line A-B of Figure 1, Figure 3 is a sectional elevation on line C-D of Figure 2, Figure 4 is a plan view of one of the contact fingers, Figure 5 is a wiring diagram of the starter with the contact plates of the drum shown flat to indicate how they approach the contact fingers whenstarting up a motor. I

According to this invention there is a top plate 1 provided with a back plate 2 a bottom resistance supporting ring 3 and abottom bearing 4. The top cover 1 is also provided with a wire outlet box 5, two stops 6 and 7 and a central bearing 8. Between the 'bottombearing 4 and the top central bearing 8 there is revolvably mounted a hollowcylindrical drum 9 of insulating material,

which has fastened thereto top and bottom journal castings 10 and 11 adapted to fit the said bearings 8 and 4 with the top journal casting 10 assing out at the top cover 1 and having a andwheel 12 attached thereto which is provided with a stop 13 arranged to limit the rotation of the hand wheel 12 to between top plate 1 sto s 6 and 7. Suitably mounted on the drum 9 there are large con-. tact plates 14g 15, and 16 in one vertical row and medium contact plates 17, 18 and 19 and small contact plates 20, 21 and 22 in another vertical row, the latter plates being connected tlogether by a wire 23 within the drum 9. e back plate 2 has a rectangular hole 24 into which is placed a panel 25 of suitable insulating material, the panel 25 bein attached by hin 26 and 27 and kept in swinging on t c said hinges (except when desired) b a simple catch 28.

Mounte sets of contact fingers the up r set 29, 30, 31, 32 and 33 situated so that t ey make con.- -tsct as desired with drum contact plates 14, 17, and 20; the middle set 34, 35, 36, 37 and 38 situated so as to make contact when desired with drum contact plates 15, 18- and 21 and the lower set 39, 40, 41, 42 and 43 situated to make contact when desired with drum contact plate 16, 19 and 22.

The contact fingers 29 to 43 inclusive are all ivoted on base pieces 44, see Figure 4 so t at they can move radially on pivot pins 45 and flat springs 46 mounted between the base pieces 44 and the said fingers keep the latter pressed outwardly so that they make good contact with the drum 9.

Mounted between top cover 1 and the bottom resistance support ring 3 and suitably insulated therefrom there are six resistance units 47, 48, 49, 50, 51 and 52. These resistances are non-inductively wound and supported on non-metallic cores. When-used in starting large motors the resistances may be situated in separate containers.

The whole of the mechanism on the under side of the top cover 1 fits into a D shaped tank 53 which is kept filled with suitable oil.

The three windings 54, and 56 re resent a three phase and squirrelcage A. induction motor or other 3 phase machines started up b A. C. supply, see Figure 5,

with ends 0 windings 57, 58, 59, 60, 61-

and 62. a

The main power supply is represented by 63, 64, and which are the three phase wires of supply.

Wires connect the following Power supply 63 and finger contact-29.

Power supply 64 and finger contact 34.

Power supply 65 and finger contact 39.

Finger contact, 30-and resistance '47 and the opposite end of the latter to finger contact 31 which is also connected to resistance 48- which terminates at finger contact 32, the latter being connected to winding 55 .end 61.

Finger contact 35 is connected to resist anoe 49 the opposite end of which is connected to finger contact 36 which is also on the panel 25 there arethree ply line 63 "tion one but in 1,es7,acs

Finger contact 38 is connected to winding 55 end 58.

Finger contact- 43 is connected to winding 56 end 59.

In operation the handwheel 12 is in the direction of the arrow shown in Figplates 14 to 22 inclusive approach the contact fingers 29 to 43 inclusive as indicated by the arrow of Fi re 5.

At the first position of contact, plate 17 touches finger contacts 29 and 30, plate 20 moved ure 2 so that the drum 9 rotates and the touches contact finger 33, 18 touches 34 and 35, 21 touches 38, 19 touches 39 and 40, and 22 touches 43; the current from current supasses from finger 29 through plate 17 to n r 30 and then through resistances 47 an 48 to the winding 55 end 61, likewise current from su plyline 64 passes from finger 34 through p ate 18 to finger 35 and then through resistances 49 and 50 to winding 56 end 62 and also likewise current from supply line 65 pmes from finger 39 through plate ;19 to finger 40 and then through resistances 51 and 52 to winding 54 end 60. g

Simultaneously the opposite ends 57, 58 and 59 of windings 54, 55 and 56 are con- .nected through fingers 33, 38 and 43 to the small plates 20, 21 and 22 and as the latter are connected together by wire 23 this first point of contact has resulted in the ends 57, 58 and 59 of windings 54, 55 and 56 being connected together, with their opposite ends 60, .61 and 62 connected throu h resistances to the ower lines 65, 63 an 64 and this is a star connection of the motor with two sets of resistance to each winding.

At the second position of contact, the plates and fingers touch the same as in posiaddition plate 17 touches contact 31, plate 18 touches contact 36 and plate 19 also touches contact 41.

The current passes exactly the same as in position one except that instead of passing through finger 30 and resistance 47, likewise finger 35 and resistance 49 and also likewise plates 17 to 22 inclusive have neaaaea I I At' the third position of contact, the

Current-from the I supply 'line 63 passes from finger 29 through plate 14 to fingers 30 and 33 and from finger 30 through resistances 47 and 48 to the winding 55 and 61,

also from finger 33 to winding 54 and 57.

Current from supply line 64 passes from finger 34 through plate 15 to fingers 35 and 38 and from finger 35 through resistances 49 and to windlng 56 and 62, also from finger 38 to winding and 58.

-Current from supply line passes from finger 39 through plate 16 to fingers 40.and

43 and from finger 40 through resistances- 51 and 52' to winding 5.4 and 60 also from finger 43 to winding 56 and 59.

This has resulted in the motor being connected in delta with two sets of resistances to each winding. 5 a At thefifth position of contact the plates and fingers touch as inthe fourth position Y but in addition plate 14 touches fin er 31,

'- will be ve plate 15 ,touches finger 36 and p ate 16 .touches finger 41 and this results in the motor being connected in delta but with one resistance unit'47, 49 and 51 being cut out of each winding 55, 56 and 54 respectively.

At the sixth position which is also the last where the handwheel 12 is prevented from further rotation by its stop 13 comin up againsttop plate sto 7, the plates an fin rs touch as in the fth position but in .ad ition plate 14 touches finger '32, plate 15 touches finger 37 and plate 16 touches finger and results in all resistances 47 .to.52 1nclusive being cut out and the motor running in delta without any resistance. 'It has been found that when starting in delta, eliminating the star connection and;usin the series resistances, the curren t-at stan still will be about the same as that when using a-compensator but the starting period much shorter so that-thelpower consumed or starting will be materia less with equal or better startingtorque. I ith the present type of starter the current rush is not so great as that when usinga com sator, for the motor is not disconnected m the line when shifting from starting to runnirag position.

aims.-

1. In combinationwith a polyphase alternating current motor, a source of current, a

starter comprising limiting resistances, and means for connecting the stator windings of said motor in star to said source of current supply and simultaneously insertin said limiting resistances in series with eac of said windings, removing'said resistances from said star connection, then connecting the stator windings of said motor in delta to said source .of current su ply and simultaneously inserting said limiting resistancesv in series with each of said stator windings,

and then removing said resistances from said delta connection to permit the motor to run in straight delta.

2. In combination with a polyphase alter-- nating current motor, a sourcepf current, a starter comprising limiting resistances, and means for connecting .the stator windings of said motor in star to said source of current supply and simultaneously inserting said limiting resistances in series with each of said windings, successively removing portions of said resistances until all of the resistances have been removed from said star connection, then connecting the stator wmdings of said motoriin delta to said source of current supply and simultaneously inserting said limiting resistances in series with each of said stator windings, and then successively removing portions of said resistances until all ofthe resistances'have been removed from said delta connection and the motor is running in straight delta.

3. In combination with a polyphase alternating current motor, a source of current, a startercomprising limitin resistances, and a switch provided with a p urality of spaced insulated contact members, said contact members being brought into operative position in sequence to connectthe stator windings of said motor in star. to said source of current supply. and simultaneously insert of said windings, successively remove portions of said resistances'until all of the resaid limiting resistances in series with each sistances'have been removed'from said star connection, then connect the stator windings of said motor in delta to said source of current supply and simultaneously insert said limiting resistances in series with each of saidstator windings, and then successively remove-portions of said resistances until all of the resistances have been removed from saiddelta connection and the motor is running in straight delta.

In testimony whereof I aflix my signature,

' .HELIER OSWALD BREE. 

